Many times. I very much try to pick adults. On occasion I will friend a minor, not often.
If upon reviewing their profile they don't have many posts or are below 15 in levels I'll not friend them either.

Just as I chose my friends in real life, I like to know something about them.

Yes I do if I use the, "See how you match" feature and find that someone gives the opposite answer from me on questions about issues that I consider most important. I also look on people's profiles before accepting friend requests and if we have a lot different I will also reject the friend request.